Your dentist will take an impression of your teeth and ask the laboratory to make a custom made tray. He will then show you how to place the whitening gel into the tray and will go through the whole technique with you.
The ‘active ingredient’ in the product is usually hydrogen peroxide or carbamide peroxide. As the active ingredient is broken down, oxygen gets into the enamel on the teeth and the tooth colour is made lighter.
Witney Dental Practice Updated June 2020 :)